The use of disposable cup lids on disposable, single use hot drink cups, has been known for many years. The disposable cup lids are generally vacuum formed from thin sheets of extruded polystyrene plastic. Other thermoformed sheet plastics materials may also be used. The lids are formed using thermo- and vacuum-forming machines, whereby the thin polystyrene sheet is pulled down over or into a male or female mold, respectively, cooled, stripped from the mold, and stamped or die cut so as to form discrete cup lids. In the North American markets alone, and in the European markets, literally millions of such disposable cup lids are manufactured for single use purposes, used in the respective hot drink markets, and then disposed of, every day.
It has been known for some time that, when the thin sheet of polystyrene plastic is extruded, an orientation grain is formed in the sheet of polystyrene material. The orientation grain acts in such a manner that the polystyrene material can be torn easily in a direction along the orientation grain, but is much more difficult to tear or fracture in a direction perpendicular to or otherwise at an angle to the orientation grain. This fact, in turn, in taken advantage of in manufacturing disposable cup lids especially for use with hot drinks, whereby a so-called "foldback cup lid" is formed. In this manner, a drink-through portion can be formed in the cup lid when the purchaser of the hot drink desires to consume that beverage.
The drink-through portion of the cup lid is generally a small portion formed at the periphery thereof and extending more or less radially but more generally along the extrusion lines formed in the material of the cup lid, into the interior cover or panel portion of the cup lid. This permits an opening to be formed in the lid, whereby the cup with that opening formed in its lid may be brought to the mouth of the user, and the beverage consumed. Moreover, the configuration of a drink-through lid also permits the lid to otherwise remain in place over the major portion of its area, thereby retaining steam or warm vapour within the confines of the covered cup and thereby reducing the rate at which the beverage will cool.
However, whenever a drink-through portion of a cup is formed by peeling back or tearing out a small portion of the cup lid, such a step involves breaking or tearing the rim or skirt of the cup lid, across a small portion thereof, and then tearing or folding back the rim and the adjoining portion of the panel of the cup lid. This, in turn, results in sharp edges at each side of the opening or gap thereby formed in the rim or skirt of the cup lid. Very often, however, those sharp edges may be uncomfortable to the lips and/or the tongue of the user. This, in turn, may tend to negate the purpose for the foldback portion of the cup lid because if the user rejects the discomfort due to the sharp edges defining the drink-through portion, then the user may simply opt to discard the cup lid in its entirety. This, in turn, will lead to faster cooling of the hot drink, and prospectively as well to an increased risk of spillage.
Moreover, particularly with drink-through lid having a foldback portion, it is not uncommon for the foldback portion to be not well retained in its folded back configuration, due at least in part to the elastic memory characteristic of the material of the cup lid, so that that folded back portion may be awkwardly in place in such a manner that it may interfere with the upper lip or even the nose of the user as she or he attempts to drink a beverage from the cup. This also may result in a decision by the user, therefore, simply to opt to discard the cup lid in its entirety.
The present inventor has discovered, quite unexpectedly, that an improved cup lid having a drink-through portion can be provided, presenting advantages over prior art cup lids which otherwise provide drink-through lids, by configuring the rim of the cup lid, and the central panel thereof, in manners to be described in greater detail hereafter.